Method for producing tank

ABSTRACT

Provided are a method for producing a tank with an outer surface profile that allows a thin label to be easily and firmly attached to a surface thereof, and also such a tank. The method for producing the tank, which includes winding fiber bundles containing an uncured resin component in multiple layers around the outer surface of a liner in a first pitch width so as to form a fiber reinforced resin layer, further includes: winding fiber bundles in a second pitch width wider than the first pitch width so as to form a gap with a required width where no fiber bundle is present between adjacent fiber bundles in winding the fiber bundles to form an outermost layer; shaving off a tip end portion of a projection made of a resin that has cured after bleeding into the gap, with a portion of the projection in a predetermined height left unshaved; and attaching a label to a surface obtained through shaving off the tip end portion.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent applicationJP 2017-005411 filed on Jan. 16, 2017, the content of which is herebyincorporated by reference into this application.

BACKGROUND Technical Field

The present disclosure relates to a method for producing a tank, inparticular, a tank that is shaped such that the outer surface of a linerthereof is covered with a fiber reinforced resin layer, and relates tothe tank.

Background Art

As a method for producing a high-pressure tank used for storage orsupply of hydrogen or the like, there is known a method that includeswinding fiber bundles containing an uncured resin component, such asCFRP, around the outer peripheral surface of a liner in a predeterminedpitch width, and then curing the resin so as to form a fiber reinforcedresin layer. JP 2013-167298 A describes attaching, to a cylindrical bodyof the high-pressure tank produced in the aforementioned manner, a thinlabel with relevant information, such as the producer, date ofproduction, and fuel type, written thereon.

Further, J P 2011-144860 A describes a method for producing ahigh-pressure tank that has a step of winding fiber bundles containingan uncured resin component around the outer surface of a resin liner ina predetermined pitch width so as to form an uncured fiber reinforcedresin layer, the method including a step of applying a solvent to anuncured surface resin layer, which has been formed through bleeding ofthe uncured resin component of the uncured fiber reinforced resin layerto the outside, to allow the solvent to infiltrate the uncured surfaceresin layer, and a step of performing heating treatment for foaming thesurface resin layer to make it porous through removal of the solvent byevaporation as well as curing the resin component of the uncured fiberreinforced resin layer.

SUMMARY

FIG. 7 is a schematic partial view of a high-pressure tank producedusing the method for producing a high-pressure tank described in JP2013-167298 A or JP 2011-144860 A, the method including winding fiberbundles containing an uncured resin component around the outer surfaceof a liner in a predetermined pitch width so as to form an uncured fiberreinforced resin layer. In FIG. 7, reference numeral 1 indicates a linerand the outer surface of the liner 1 has formed thereon a fiberreinforced resin layer 2 of the fiber bundles wound therearound.Further, the outer surface of the fiber reinforced resin layer 2 has asurface resin layer 3 formed thereon. The surface resin layer 3 is alayer solely made of an excess resin that has bled to the outside informing the fiber reinforced resin layer 2 through winding of the fiberbundles impregnated with the uncured resin around the liner 1.

In the actual high-pressure tank produced in the aforementioned manner,the surface of the surface resin layer 3 is not flat. This is becausethe surface obtained after the bleeding resin is cured is a roughsurface with many projections in different sizes irregularly presentthereon, since the resin bleeds from the fiber bundles randomly andirregularly both in the amount and site.

A high-pressure tank is usually required to have attached thereto alabel with relevant information, such as the producer, date ofproduction, and fuel type, written thereon, as described above. However,when the label is attached to a rough surface, the state of the attachedlabel is unstable. Therefore, in attaching the label to the surface, itis necessary to shave off tip end portions of the aforementionedprojections to obtain a substantially flat surface.

Further, the surface resin layer 3 is, in most cases, a transparentresin layer and thus has high light transmission. Therefore, it isdifficult to accurately identify the shape of the rough surface and thepositions of projections on the surface using laser or the like, and theactual operation of shaving off the tip end portions is manuallyperformed while the shape is visually and tactually checked.

The work load of such operation is significant in producing thehigh-pressure tank. Furthermore, at the time of attachment of the label,it is necessary to apply an adhesive to the flat surface obtainedthrough shaving off the tip end portions, and there is also a problem inthat after the attachment of the label, an unnecessary item, such as abacking sheet for the label, is generated.

The present disclosure has been made in view of the foregoingcircumstances, and provides a method for producing a tank, the methodincluding winding fiber bundles containing an uncured resin component inmultiple layers around the outer surface of a liner in a first pitchwidth so as to form an uncured fiber reinforced resin layer, whichallows the tank to have an outer surface profile in which an appropriatethin label can be easily and firmly attached to the surface of the tank.The present disclosure further provides the tank with such an outersurface profile.

The method for producing a tank according to the present disclosure is amethod that basically includes at least winding fiber bundles containingan uncured resin component in multiple layers around the outer surfaceof a liner in a first pitch width so as to form a fiber reinforced resinlayer, the method including: forming one or more regions where fiberbundles are wound in a second pitch width wider than the first pitchwidth so as to form a gap with a required width where no fiber bundle ispresent between adjacent fiber bundles in winding the fiber bundles toform at least an outermost layer; and shaving off a tip end portion of aprojection made of a resin that has cured after bleeding into the gap,with a portion of the projection in a predetermined height leftunshaved.

According to the method for producing a tank, attachment of the thinlabel to the outer surface of the tank produced is easily performed andthe state of the attached label is stable.

In a preferred embodiment of the method for producing a tank, the tipend portion is shaved off so that the portion left unshaved has a flatsurface. Further, in another preferred embodiment, the method forproducing a tank further includes forming a light reflecting layerthrough application of a material for forming the light reflecting layeron at least a surface of the projection and determining the position andshape of the projection through irradiating the light reflecting layerwith laser, in which the tip end portion is shaved off based on theinformation obtained from the determination. In yet another preferredembodiment of the method for producing a tank, a material containing anadhesive is used as the material for forming the light reflecting layer.

In a preferred embodiment, the method for producing a tank furtherincludes attaching a thin label to the surface obtained through shavingoff the tip end portions. Further, in another preferred embodiment ofthe method for producing a tank, the one or more regions where the fiberbundles are wound in the second pitch width is/are present in at least acylindrical body of the tank.

The tank according to the present disclosure is a tank that has a fiberreinforced resin layer formed through winding fiber bundles containingan uncured resin component in multiple layers around the outer surfaceof a liner, in which at least the outermost layer of the fiberreinforced resin layer has one or more regions where a gap where nofiber bundle is present between adjacent fiber bundles is formed, theresin that has cured after bleeding is present in the gap, and the topsurface of the resin that has cured is a flat surface.

In a preferred embodiment of the tank, an adhesive is applied to theflat surface thereof. Further, in another preferred embodiment of thetank, the one or more regions where the gap is formed is/are present inat least the cylindrical body of the tank. In yet another preferredembodiment of the tank, a thin label is attached to the aforementionedflat surface.

According to the present disclosure, it is possible to obtain a tankthat has a fiber reinforced resin layer on the outer surface of a linerthereof, in which a thin label can be easily and surely attached to thesurface of the tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an example of a high-pressure tank;

FIG. 2 is a first view for illustration of an operation procedure of anembodiment;

FIG. 3 is a second view for illustration of an operation procedure ofthe embodiment;

FIG. 4 is a third view for illustration of an operation procedure of theembodiment;

FIG. 5 is a fourth view for illustration of an operation procedure ofthe embodiment;

FIG. 6 is a fifth view for illustration of an operation procedure of theembodiment; and

FIG. 7 is a partial view anon of the structure of a conventionalhigh-pressure tank.

DETAILED DESCRIPTION

An embodiment of the present disclosure will be described below withreference to the drawings.

FIG. 1 is a schematic view of an example of a tank. In this example, atank 10 is a high-pressure tank that is adapted to be filled with ahigh-pressure hydrogen gas and mounted on a fuel cell vehicle. However,the tank 10 may be used for any purposes, and the filling is not limitedto a high-pressure hydrogen gas.

In this example, the high-pressure tank 10 includes a cylindrical body17 with opposite ends in a round dome shape, a gas barrier liner 11, anda fiber reinforced resin layer 12 including a surface resin layer 13.Further, the high-pressure tank 10 has openings formed at the oppositeends thereof, and one of the openings has attached thereto a mouthpiece14 with a valve 15, and the other has attached thereto an end boss 16.The cylindrical body 17 forms the center portion of the high-pressuretank 10.

The liner 11 is a resin member that defines an accommodation space 18 tobe filled with, for example, a high-pressure hydrogen gas. Typically,the liner 11 is made of a thermoplastic resin that can be processed intoa substantially cylindrical shape or the like. The resin that forms theliner 11 is preferably a resin that can be easily processed and has aproperty of retaining a hydrogen gas within the accommodation space 18,that is, a resin that is excellent in the gas barrier property. Examplesof such a resin include a thermoplastic resin, such as polyester,polyamide, polyethylene, and ethylene vinyl alcohol copolymer (EVOH).

The liner 11 is in a substantially cylindrical shape with the domeportions at the opposite ends of the cylindrical body 17 as describedabove. Each of the dome portions of the liner 11 has an opening formedtherein as described above, and the openings in the dome portions at theopposite ends are provided with the mouthpiece 14 and the end boss 16,respectively. The fiber reinforced resin layer 12 is formed along theouter surface of the liner 11.

The fiber reinforced resin layer 12 is a layer that covers the outersurface of the liner 11 and has a function of reinforcing the liner 11to improve the mechanical strength of the high-pressure tank 10, such asthe rigidity and pressure resistance. The fiber reinforced resin layer12 includes a thermosetting resin and reinforced fiber bundles. As thethermosetting resin, it is preferable to use a phenol resin, melamineresin, urea resin, epoxy resin, and the like, of which the epoxy resinis, in particular, preferably used from the viewpoint of the mechanicalstrength and the like. As the reinforced fibers, glass fibers, aramidfibers, boron fibers, carbon fibers, and the like can be used, and thecarbon fibers are, in particular, preferably used from the viewpoint ofthe lightness, mechanical strength, and the like.

Typically, an epoxy resin is obtained through mixing and thermallycuring a prepolymer, such as a copolymer of bisphenol A andepichlorohydrin, and a curing agent, such as polyamine. The epoxy resinis fluid in an uncured state, but after thermally cured, the epoxy resinforms a strong cross-linked structure so as to become insoluble in asolvent, such as methyl ethyl ketone (MEK).

The fiber reinforced resin layer 12 is formed such that bundles offibers (for example, carbon fibers) impregnated with an uncured resin(for example, an epoxy resin) are wound around the outer surface of theliner 11 in multiple layers in a given pitch width (hereinafter referredto as a first pitch width a), and the resin is then cured. For example,a shaft is attached to the mouthpiece 14 and end boss 16 of the liner 11and is rotatably supported, and fiber bundles impregnated with resin arewound while the shaft is being rotated. Then, heating is performed atthe curing temperature of the resin to cure the resin component. Helicalwinding or hoop winding is adopted for winding of the fiber bundles. Thefirst pitch width a is typically set to a value almost equal to thewidth of each of the fiber bundles to be used.

In winding the fiber bundles impregnated with resin in multiple layers,as shown in FIG. 2, when the fiber bundles are wound to form at least anoutermost layer 20 of the fiber reinforced resin layer 12, the fiberbundles are wound around some regions in a second pitch width b widerthan the first pitch width a. The region where the fiber bundles arewound in the second pitch width b may be any region, but is preferablythe cylindrical body 17 of the high-pressure tank 10,

FIG. 2 to FIG. 6 are schematic enlarged views of a region indicated by Ain FIG. 1 of the high-pressure tank 10 of the present embodiment. Inthis example, a portion 12 a other than the uppermost layer 20 of thefiber reinforced resin layer 12 is entirely wound with the fiber bundlesimpregnated with an uncured resin in multiple layers in the first pitchwidth a, for example. Herein, the first pitch width a is almost equal tothe width of each of the fiber bundles.

In winding the fiber bundles to form the uppermost fiber bundle layer20, the fiber bundles impregnated with resin are wound in the secondpitch width b wider than the first pitch width a in a region where alabel is to be attached after completion of the high-pressure tank. Inan example shown in FIG. 2, the second pitch width b is “the first pitchwidth a plus the width c of the gap.” As an example, the first pitchwidth a and the second pitch width 11 are typically around 12 to 20 mmand around 20 to 24 mm, respectively.

Through winding the fiber bundles to form the uppermost fiber bundlelayer 20 in the aforementioned manner, in the uppermost layer 20, aportion where the fiber bundles are wound in the first pitch width a hasthe fiber bundles arranged in rows substantially with no gap between thefiber bundles, while in a region where the fiber bundles are wound inthe second pitch width b, as shown in FIG. 2, a gap with the width cwith no fiber bundle present therein is formed between adjacent fiberbundles. In the experiment conducted by the present inventors, anintended purpose was able to be achieved when the width c of the gap wasset to around 0.25 to 0.5 times the width of the fiber bundle as 1.

It should be noted that in the example shown in the drawings, winding ofthe fiber bundles in the second pitch width b is performed only in theuppermost fiber bundle layer 20, but also in some of the layers belowthe uppermost layer, the fiber bundles may be wound in the second pitchwidth b in some portions. However, in that case, the layers arepreferably formed through winding the fiber bundles so that the gapswith the width c where no fiber bundle is present in the layers areradially aligned relative to the central axis of the tank.

In the fiber reinforced resin layer 12 that is formed through windingthe fiber bundles impregnated with an uncured resin (for example, anepoxy resin) in multiple layers, the surface resin layer 13 is formedthrough bleeding of the uncured resin to the outside as shown in FIG. 1,As described above, typically, the surface of the surface resin layer 13is not flat, and is a rough surface with many projections in differentsizes irregularly present thereon, because the resin bleeds from thefiber bundles randomly and irregularly both in the amount and site. Itshould be noted that in FIG. 2 to FIG. 6, the surface resin layer 13 isnot shown for easy understanding.

In the high-pressure tank 10 of the aforementioned embodiment, asdescribed above and shown in FIG. 2, the uppermost layer 20 of the fiberreinforced resin layer 12 has a gap with the width c where no fiberbundle is present between adjacent fiber bundles in some portionsthereof. Therefore, the uncured resin that has impregnated the fiberbundles bleeds more into each of the gaps with the width c that has nofiber bundle present therein and has less resistance as compared toother regions. Then, the bleeding resin projects in a chevron shape fromthe gaps with the width c radially relative to the central axis of thetank so that projections 30 are formed, as shown in FIG. 3. It should benoted that through appropriately adjusting the amount of resin thatimpregnates the fiber bundles and the width c of the gap, that is, thesecond pitch width b, the height of each of the projections 30 that areformed through curing of the bleeding resin can be appropriatelyadjusted. The optimum values may be experimentally determined.

With the aforementioned state, the resin is cured. However, each of theprojections 30 made of the cured resin has a round top portion and thusis not suitable for attaching a thin label thereto. Therefore, the tipend portion of each of the projections 30 is shaved off by means of anappropriate means with a portion thereof in a predetermined height leftunshaved. More preferably, each of the tip end portions is shaved off soas to obtain a flat surface. It should be noted that, as describedabove, each of the projections 30 of the bleeding resin is made of atransparent thermosetting resin and has high light transmission.Therefore, it is extremely difficult to perform mechanical processing ofshaving off the tip end portions of the projections 30 based on theinformation obtained through reading the shapes of the projections usinglaser irradiation.

Therefore, in the present embodiment, a step of applying of a materialfor forming a light reflecting layer to the region where the fiberbundles are wound in the second pitch width b so as to form a lightreflecting layer 40 is further performed. It is preferable, from theviewpoint of operability, to apply the material to the entire regionwhere the fiber bundles are wound in the second pitch width b, butapplying the material only to at least the surface portions of theprojections 30 can also achieve an intended purpose.

Examples of the “material for forming a light reflecting layer” includematerials containing metal powder, of which a titanium oxide isparticularly preferred. FIG. 4 shows the state of the light reflectinglayer 40 that has been formed through application of the material forforming the light reflecting layer. With the thickness of the lightreflecting layer 40 of around 20 μm, for example, an intended purposecan be sufficiently achieved.

With the light reflecting layer 40 formed, the shapes and positions ofthe projections 30 can be determined using laser, and the tip endportions of the projections 30 can be mechanically shaved off so as toobtain an appropriate shape based on the obtained information. FIG. 5shows the state after the tip end portions are shaved off. In thisexample, through mechanically shaving off the tip end portions, thesurface of the portion left unshaved becomes a flat shaved surface 50.Through obtainment of the flat shaved surface 50, as shown in FIG. 6, itbecomes possible to easily attach a thin label 60 to the surface.

As the label 60 to be attached, a label provided with an adhesive orcohesive layer on the backside thereof may be used. Further, it is alsopossible to attach a label with no adhesive layer on the backsidethereof after application of an adhesive to the shaved surface 50. Inboth cases, since the shaved surface 50 is flat, the operation ofapplying an adhesive to the shaved surface 50 is easily performed, andattachment of the label 60 after the application of the adhesive is alsofacilitated. Further, since the interface for the attachment is a flatsurface, a stable attachment state can be obtained.

In an aspect of the aforementioned embodiment, a material mixed with anadhesive is used as the material for forming the light reflecting layer40. Examples of the adhesive to be mixed may include materials, such asan epoxy resin, modified silicone, urethane resin, acrylic resin, andcyanoacrylate, of which the epoxy resin is particularly suitable. Withthe use of the material mixed with the adhesive, it is unnecessary toadditionally use the adhesive at the time of attachment of the label 60,so that the attachment of the label is more easily and surely performed.

As described above, according to the present embodiment, in the methodfor producing the high-pressure tank 10 that has the fiber reinforcedresin layer 12 on the outer surface of the liner 11 thereof, it ispossible to produce the high-pressure tank 10 that allows the thin label60 to be easily and surely attached to the surface of the tank. Further,it is possible to obtain the high-pressure tank 10 in which the label isstably attached to the regions where the fiber bundles are wound in thesecond pitch width b of the produced high-pressure tank 10.

In another embodiment, in addition to the aforementioned processing, theprocessing described in JP 2011-144860 A may be further performed thatincludes a step of applying a solvent to the uncured surface resin layer13, which has been formed through bleeding of an uncured resin componentof the uncured fiber reinforced resin layer to the outside, to allow thesolvent to infiltrate the uncured surface resin layer 13, and a step ofperforming heating treatment for foaming the surface resin layer 13 tomake it porous through removal of the solvent by evaporation as well ascuring the resin component of the uncured fiber reinforced resin layer.A method for producing a tank that further includes the aforementionedmethod and a tank produced using the method are also encompassed by thepresent disclosure.

In that case, it is preferable to use as the solvent a solvent that ishighly compatible with an uncured resin and that has a lower boilingpoint than the heating temperature at the time of performing thermalcuring. When an epoxy resin is used as the resin for forming the fiberreinforced resin layer 12 (surface foamed resin layer 13), methyl ethylketone (MEK), toluene, dimethylacetamide, acetone, and the like may beused, and in particular, it is preferable to use MEK. Further, thecompatibility and evaporation temperature may be adjusted through mixingof two or more solvents.

DESCRIPTION OF SYMBOLS

-   10 High-pressure tank-   11 Liner-   12 Fiber reinforced resin layer-   18 Accommodation space-   20 Uppermost layer of fiber reinforced resin layer-   30 Projection of cured resin-   40 Light reflecting layer made of material for forming light    reflecting layer-   50 Flat shaved surface-   60 Attached thin label-   a First winding pitch width of fiber bundles-   b Second winding pitch width of fiber bundles-   c Difference between second winding pitch width and first winding    pitch width (gap between fiber bundles)

1-6. (canceled)
 7. A tank including a fiber reinforced resin layerformed through winding fiber bundles containing an uncured resincomponent in multiple layers around an outer surface of a liner,wherein: at least an outermost layer of the fiber reinforced resin layerhas one or more regions where a gap where no fiber bundle is presentbetween adjacent fiber bundles is formed, a resin that has cured afterbleeding is present in the gap, and a top surface of the resin that hascured is a flat surface.
 8. The tank according to claim 7, wherein theflat surface is provided with an adhesive property.
 9. The tankaccording to claim 7, wherein the one or more regions where the gap isformed is/are positioned in at least a cylindrical body of the tank. 10.The tank according to claim 7, wherein a thin label is attached to theflat surface.